why doesn't use threading?

[renzhexigua]

fetch 300 proxies. 80~110 valid ip.
number of process to check validity and time cost below
1 -> Total time running loadSlave: 387.08184909820557 seconds
2 -> Total time running loadSlave: 190.975604057312 seconds
4 -> Total time running loadSlave: 101.29392600059509 seconds
8 -> Total time running loadSlave: 53.29184103012085 seconds
12 -> Total time running loadSlave: 37.38354516029358 seconds
16 -> Total time running loadSlave: 28.30510187149048 seconds
20 -> Total time running loadSlave: 25.23692011833191 seconds
24 -> Total time running loadSlave: 22.36588215827942 seconds
28 -> Total time running loadSlave: 19.992196083068848 seconds
32 -> Total time running loadSlave: 18.461107969284058 seconds
36 -> Total time running loadSlave: 17.572476863861084 seconds
40 -> Total time running loadSlave: 17.44138479232788 seconds
44 -> Total time running loadSlave: 16.960041999816895 seconds